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Exercise Title:
Visualizing Historical and
Near-Real-Time (NRT) Satellite-Measured
Surface
Temperatures in Integrated Data Viewer (IDV): Group for High
Resolution Sea Surface Temperature (GHRSST) Products via FTP
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Abstract: This exercise demonstrates how to get
global, remotely sensed SST data products in easily usable grids
(i.e. L3 or L4 NetCDF). the principal method is via full file
downloads, followed by standard visualization methods in IDV. Users
can optionally subset the grids in IDV for easier use, and economical local
storage. The emphasis of this exercise is to provide real-time (or very
nearly so) products. But the GHRSST project system also supports
historical data, through the same technical system. Users of both
operational and historical data can refer here to the very best
international sources and products. In all cases, the data must be
downloaded via FTP methods. As various product systems evolve
toward direct connection, via OPENDAP technology, they will be migrated
to their own, separate MDL exercises.
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MUR SST products are covered
elsewhere because they are available through OPENDAP and they are often
provided one day faster than the methods used below. The choice is
up to you, depending on what you need.
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G1SST
products are covered elsewhere
because they derive from a blend of satellite, in-situ and modeled
results
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Preliminary Reading (in
OceanTeacher, unless otherwise indicated):
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Required Software:
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Other Resources:
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Author: Murray
Brown
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Version: 9-28-2015
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1. Open the GHRSST website, and take some time to read
through this very useful program.
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2. Select
PRODUCTS & SERVICES to see what's available.
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3. The GHRSST
provides both historical data and operational data, which only you can
decide to follow. Here in MDL we'll go after the operational data,
because this is the OPS section of MDL. The same methods pertain to
the historical data. |
4. If you click on HISTORICAL DATA, you'll find this
list of robust sources. It seems that all desirable methods are
available for you. The best method, OPENDAP, is not available for us
below, so be prepared for the old traditional data download method.
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5. And here's the list of methods to get REAL TIME DATA. Spend
some time here and follow these links. Try to get your own impressions
of exactly what's there and how the methods are presented.
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6.
Concerning these apparent 5 routes to the data, fully named in the NOTES
above, we have these comments:
- GHRSST MMR System - This is just a link to pass you off to a
separate JPL catalog of many of the same access methods mentioned on the
referring page
(including the FTP). It includes a link to an
"OPENDAP Interface" to GHRSST products, which does publish
usable URL's for use in IDV. But unfortunately many of them are
for dates up to 2 months prior, so this is not a reliable source for
true operational purposes.
- GDAC FTP Site - The old tried-and-true method to download
files from a (hopefully) well-organized archive.
- We'll pursue this method
for everything except the
MUR
and
G1SST
products, covered elsewhere in MDL by valid OPENDAP methods
- RDAC Local Servers - Not further followed by MDL
- HR-DDS Data Granules - Not further followed by MDL
- MDB Records - Not further followed by MDL
The author hopes that someday, ALL these products will be available via
reliable OPENDAP service. But for now, we'll have to focus on the GDAC
FTP Sites. |
7. Here's the route we'll follow to the data, in MDL. You are
encouraged to explore everything on your own later. Basically, we want
fully developed grids (L4) of the whole earth (GLOB), that are
near-real-time (NRT).
- FTP (be adventurous, explore them all!)
- GDS2
- L2P
- L2P GRIDDED
- L3P
- L4
- AUS
- GAL
- MED
- NCAMERICA
- NSEABALTIC
- NWE
- GLOB
- JPL
- MUR
- Covered elsewhere in MDL
- JPL_OUROCEAN
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G1SST
- Covered elsewhere in MDL
- EUR - Not NRT
- REMSS - Not NRT
- ABOM
- GAMSSA 28km - Global file labeled "Sep 27" on
Sept 27; see below
- NAVO
- K10 SST - Global file labeled "Sep 26" on
Sept 27
- NCDC
- AVHRR OI - Global file labeled "Sep 26" on
Sept 27
- UKMO
- OSTIA - Global file labeled "Sep 26" on Sept
27
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8. Download the 4 bottom zipped files to a convenient location, e.g.
LIBERIA > DATA > OCEAN > GHRSST |
9. Run IDV. |
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10. Select DATA CHOOSERS > FILES than navigate to the files folder. |
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11. Select all the files you want to show. It is very important to specify the Data Source Type, because these are
zipped files. Then click ADD SOURCE. |
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12. Now you have the files ready to work with in IDV.
Right-click on the first one, and select PROPERTIES. |
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13. First, to keep track of which file this is, select the PROPERTIES
tab, and change the name to something simple and logical, as you see here.
In real work, you should use a
longer name to identify the date, etc. etc. |
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14. Second, (because these are global files) we need to select SPATIAL
SUBSET. Draw an arbitrary square over the Atlantic to activate the
tool. Then enter the desired Liberia values in the tool, as you see here. |
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15. Now you can make these choices for a good visualization; try other
options on your own, later. Click CREATE DISPLAY.
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16. Above, you named the data file. To name the actual display
image, use these two steps. Select EDIT > PROPERTIES. |
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17. Then select DISPLAY LABEL and enter a good logical name.
Here we used the same name as above. Click APPLY.
This is how to you can make much
better labels for IDV, which automatically makes names that are usually too
long and don't differentiate very well. |
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18. Now you have a well named, clear visualization of the ABOM
temperature grid.
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19. In real-world work you might want to compare the 4 grids, which
you can do later on your own. To do this, all 4 grids must be
displayed with the same temperature value ranges. Here's how to do
that. |
20. Go back to the PROPERTIES tool, and select COLOR TABLE > DEFAULT >
CHANGE RANGE. Enter values that you already know will cover the lowest
low and the highest high from all the grids.
Here we've entered crude guesses of 290 to 305. [When you see the
visual result below, you'll agree the range is too big.]
Then click OK. |
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21. You should also use a better palette, and the author recommends
COLOR TABLE > DEFAULT > RADAR > DBZ. |
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22. This looks ugly, but it's a good beginning. Check all 4
grids for the highest high and lowest low, and you'll have a much smaller
range to use. The final images should be much better. |
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23. When you have studied these products, you may have favorites, etc.
So make specific plans and methods for capturing and displaying the images
you need for your own work. Assume other students or lab workers will
make these, so keep the instructions very clear and logically arranged. |